Lookup stage "from": "$colName", but it doesn't work

Working with Data
1

Hi, I try to use in aggreagation lookup stage “from”: “$colName”, but it doesn’t work
Any suggestion will be help …

        {
            "$match": {
                "_id": new ObjectID("651aff11fa62127802083116")
            }
        }, 
        {
            "$project": {
                "colName": "col",
                "constantId": "$meta.constantId"
            }
        }, 
        {
            "$lookup": {
                "from": "$colName", // doesn't work
                "from": "col", // work
                "localField": "constantId",
                "foreignField": "facilityConstantId",
                "as": "array"
            }
        }
3

Hi @Nurlan_Kazdayev,

Whats the use case details / requirements of passing that from the $project value in as opposed to just using "col" for the single $lookup stage you provided?

Look forward to hearing from you.

Regards,
Jason